In group 13, the only metalloid, boron, is at the very top of the group. Explain why the rest of the group has metallic behavior but boron does not.

Answer:

Boron is at the top of group 13 and has only two electron shells. Because it has fewer shells, the nucleus has a stronger pull on valence electrons, making it more likely to share or gain electrons rather than lose them compared to elements further down the group. While all group 13 elements have three valence electrons and could lose them to behave like metals, boron's small size leads to it having properties of both metals and nonmetals, classifying it as a metalloid. The elements below boron have more electron shells, meaning their valence electrons are further from the nucleus and more easily lost, resulting in metallic behavior.